1. Field of the Invention
This invention relates to computer networks. In particular, the invention relates to network telephony.
2. Description of Related Art
Packet-based data networks are widely used to link various nodes, such as personal computers, servers, gateways, and so forth. Packet-based data networks include private networks, such as local area networks (LANs), Metropolitan Area Networks (MANs), Wide Area Networks (WANs), and public networks, such as the Internet. The increased availability of such data networks has increased accessibility among nodes, whether the nodes are located in close proximity to each other (such as within an organization) or at far distances from each other. Popular forms of communications across such data networks include electronic mail, file transfer, web browsing, and other exchanges of digital data>
With the increase capacity and reliability of data networks, voice communications over data networks, including private and public networks, have become possible. Voice communications over packet-based data networks are unlike voice communications in a conventional public switch telephone network (PSTN), which provides users with dedicated end-to-end circuit connections for the duration of each call. Communications over data networks, such as IP (Internet Protocol) networks, are performed using packets that are sent in bursts from the source to one or more destination nodes. To enable voice communications between end points on a data network, a virtual circuit connection is established between the end points. Voice data sent over a data network has to share the network bandwidth with conventional non-voice data (e.g., electronic mail, file transfer, web access, and other traffic). One standard that has been implemented for communications of voice as well as other data is the H.323 recommendation from the Telecommunications Sector of the International Telecommunication Union (ITU-T), which describes terminals, equipment and services for multimedia communications over packet-based networks.
In an IP data network, each data packet is routed to a node having destination IP address contained within the header of each packet. Data packets may be routed over separate network paths before arriving at the final destination for reassembly. Transmission speeds of the various packets may vary widely depending on the usage of data networks over which the data packets are transferred. During peak usage of data networks, delays added to the transfer of voice data packets may cause poor performance of voice communications.
Despite the increasing popularity of communicating over IP data networks, several applications have presented difficulties to the integration of IP telephony in a traditional communication environment. One example is the Enhanced 911 (E911) emergency call. The E911 regulatory requirements require location information concerning where the 911 caller is located. With a switched network this problem was solved by the transmission of the caller's telephone number to a Public Safety Answering Point (PSAP) where it was cross-referenced with an address database to determine the caller's location. That information was then displayed on a video monitor for the emergency dispatcher to direct public safety personnel responding to the emergency. This enabled emergency organizations to find callers who could not orally provide their precise location. Although this problem has been solved for conventional public switched telephone systems such as in a public switched telephony network, the problem still exists for data networks, and in particular, location identification using IP telephony. First, the IP telephones are not tied or physically connected to a geographical location and thus their locations may be dynamic. Second, the information retrieval is not scaleable because there are a large number of IP domains and service provider policies (e.g., telephone companies, cable companies, and cellular companies).
A further issue is that congestion on the data network may slow emergency communications traffic. Thus there is a need for prioritization of the emergency traffic to ensure a high degree of quality of service.
Since each IP address has no geographic association, there is no provision for locating a network resource such as a server, a router, a gateway, or an IP terminal. If a fault occurs in a network resource, there is no way of geographically locating that resource. Thus, it would be desirable to provide network resources with geographic information for the purpose of resource location. Furthermore, it would be desirable to locate the nearest network resource to a terminal in the event that the terminal cannot locate its geographic position.
In addition, IP telephony has been expensive to implement for applications involving the monitoring of environmental conditions, and remote meter reading, since each station required a dedicated connection to the IP network. Thus, there is a need for providing IP enabled applications with a communication means to communicate with a data network.
Therefore, there is a need in the art for an efficient and low-cost technique for automatic remote communication using telephony.